A team of researchers from the University of Maryland plodded through more than 6,000 Twitter postings by members of Congress to study whether the social networking site promoted transparency in politics and dialogue between elected leaders and the public.

They found -- surprise! -- that politicians spend most of their time on Twitter promoting themselves.

Launched in 2006, Twitter allows users to send succinct (no more than 140 characters) reports on their comings, goings and musings. Sixty-nine members of Congress had Twitter accounts by February. The number has since risen to 169. An estimated 21 million people tweet worldwide.

Eighty percent of the congressional Twitter postings reviewed by researchers fell into two categories: links to news articles and press releases, mostly self-serving and readily available elsewhere, and status updates that chronicle the pol's latest trip to the sawmill or the supermarket. The researchers announced their findings this week and hope to present them at an international conference on human-computer interaction in the spring.

"Twitter by its nature is a very self-absorbed service," said Jennifer Golbeck, lead researcher and assistant professor in the university's College of Information Studies. "Politicians are very self-important people."